Gearbox with sight window

ABSTRACT

A gearbox for an engine-driven mechanism comprises a gearbox housing having opposing walls. A first bearing bore is defined in one of the opposing walls and adapted for receiving an input shaft. A second bearing bore is defined in the other opposing wall and aligned with the first bearing bore. Each bearing bore mounts a bearing for supporting the input shaft which extends through the first bearing bore and into the gearbox. The second bearing bore includes an associated transparent and/or translucent lens to define a sight window for monitoring the level of oil in the gearbox. A sight window of this nature is particularly well suited for retrofitting older gearboxes which lack a sight window.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/908,118, filed Oct. 20, 2010, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/253,932, filed Oct. 22, 2009,which is hereby incorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

The present subject matter generally relates to oil level sight windowsfor gearboxes.

2. Description of Related Art

Engine-driven mechanisms require a minimum amount of a lubricant toensure proper operation of the moving parts of the drive system. In someengine-driven mechanisms, such as agricultural equipment, the drivesystem includes a gearbox containing various gears, shafts, and othermoving parts, as well as an amount of oil for lubricating the movingparts.

An exemplary prior art gearbox 10 is illustrated in FIG. 1. The gearbox10 includes a gearbox housing 12 with opposing walls 14 and 16. A pairof bearing bores 18 and 20 are defined in the opposing walls 14 and 16,respectively. The bearing bores 18 and 20 are aligned with each otherfor mounting bearings (not illustrated) to support an input shaft (notillustrated) extending through the first bearing bore 18 and into thegearbox housing 12. A metallic bore cap plug 22 is associated with thesecond bearing bore 20 to isolate the interior of the gearbox housing 12from the outside environment.

To fill the gearbox housing 12 with oil, a fill plug 24 on the top ofthe gearbox housing 12 is removed to expose a fill hole 26. Oil ispoured into the gearbox housing 12 via the fill hole 26 and the fillplug 24 is replaced once the amount of oil in the gearbox housing 12 hasreached the proper level. To ascertain the gearbox oil level, a sidewall 28 of the gearbox housing 12 is provided with a small aperture 30which receives a removable oil level plug 32. The level of oil in thegearbox housing 12 is checked by removing the oil level plug 32 andlooking inside.

It has been recognized that removing an oil level plug to check thegearbox oil level can be disadvantageous, so in some gearboxes, the oillevel plug is either replaced by or supplemented with a sight window.The sight window typically comprises the combination of an aperture inthe gearbox housing and a lens received by or otherwise associated withthe aperture. Rather than having to remove a plug to check the gearboxoil level, one merely looks through the sight window to verify the oillevel.

One problem with a typical sight window is that it can belabor-intensive to retrofit onto a gearbox having only an oil levelplug. For example, in some cases, a large aperture must be machined in awall of the gearbox housing to receive a lens.

To simplify installation of a sight window in retrofitting situations,it is known to replace the standard (i.e., opaque) oil level plug with aplug having a built-in lens, such as the GN 743 line of oil levelindicators from Elesa S.p.A. of Monza, Italy. Such oil level indicatorsavoid the problem of adding a large bore to the gearbox housing, but canbe disadvantageous in that they are small, which can make it difficultto accurately assess the gearbox oil level.

Accordingly, there remains the need for a larger oil level sight windowwhich can be easily retrofitted onto a gearbox having only an oil levelplug.

SUMMARY

There are several aspects of the present subject matter which may beembodied separately or together in the devices and systems described andclaimed below. These aspects may be employed alone or in combinationwith other aspects of the subject matter described herein, and thedescription of these aspects together is not intended to preclude theuse of these aspects separately or the claiming of such aspectsseparately or in different combinations as set forth in the claimsappended hereto.

In one aspect, a sight window is provided for a gearbox having a gearboxhousing and a pair of bearing bores. The bearing bores are aligned witheach other and defined in opposing walls of the gearbox housing. Thesight window comprises one of the bearing bores and a generallytransparent and/or translucent lens associated therewith.

In another aspect, a gearbox for an engine-driven mechanism comprises agearbox housing having opposing walls. A first bearing bore is definedin one of the opposing walls and adapted for receiving a shaft. A sightwindow comprises a second bearing bore, which is defined in the otheropposing wall and aligned with the first bearing bore, and a generallytransparent and/or translucent lens associated with the second bearingbore.

In yet another aspect, a method of providing a gearbox of anengine-driven mechanism with a sight window comprises providing agearbox and a generally transparent and/or translucent lens. The gearboxincludes a gearbox housing having opposing walls, a first bearing boredefined in one of said opposing walls and adapted for receiving a shaft,and a second bearing bore defined in the other opposing wall and alignedwith the first bearing bore. The lens is associated to the secondbearing bore to provide a sight window as a feature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a known prior art gearboxhaving an oil level plug for checking the gearbox oil level;

FIG. 2 is a front perspective view of a gearbox incorporating a sightwindow according to one aspect of the present disclosure;

FIG. 2A is an exploded perspective view of the gearbox of FIG. 2;

FIG. 3 is an exploded perspective view of a gearbox incorporating analternative sight window according to one aspect of the presentdisclosure;

FIG. 4 is a cross-sectional view of a gearbox incorporating yet anotheralternative sight window according to one aspect of the presentdisclosure;

FIG. 4A is a detail cross-sectional view of the sight window of thegearbox of FIG. 4;

FIG. 5 is a cross-sectional view of a gearbox incorporating anotheralternative sight window according to one aspect of the presentdisclosure;

FIG. 6 is a cross-sectional view of a ring member of the sight window ofFIG. 5;

FIG. 7 is a front elevational view of the ring member of FIG. 6,including a lens and other components of the sight window of FIG. 5;

FIG. 7A is a cross-sectional view of the ring member and associatedcomponents of FIG. 7, taken through the line A-A of FIG. 7;

FIG. 8 is an exploded perspective view of a gearbox incorporating yetanother alternative sight window according to one aspect of the presentdisclosure;

FIG. 9 is a perspective view of selected components of anotherembodiment of a sight window according to an aspect of the presentdisclosure;

FIG. 10 is a perspective view of a gearbox incorporating the sightwindow of FIG. 9; and

FIG. 11 is a cross-sectional view of the gearbox of FIG. 10.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The embodiments disclosed herein are for the purpose of providing therequired description of the present subject matter. They are onlyexemplary, and may be embodied in various forms. Therefore, specificdetails disclosed herein are not to be interpreted as limiting thesubject matter as defined in the accompanying claims.

FIGS. 2 and 2A show a gearbox 34 employing a sight window assembly 36according to an aspect of the present disclosure. The gearbox 34 isidentical to the gearbox 10 of FIG. 1, except that the bore cap plug 22of FIG. 1 has been eliminated and replaced with the sight window 36. Thesight window assembly 36 comprises the combination of the second bearingbore 20 and a generally transparent and/or translucent lens 38associated therewith. As used herein, the term “lens” broadly refers toa generally transparent and/or translucent piece of material (typicallyglass, plastic, safety glass, or polycarbonate) and is not limited to aparticular shape or configuration.

As shown in FIG. 2A, the wall 16 includes four threaded holes 40 spacedaround the second bearing bore 20. The lens 38 includes four holes 41adapted to align with the four threaded holes 40 when the lens 38 isplaced against the wall 16. Each hole 41 of the lens 38 receives athreaded fastener 42 which is mated with the corresponding threaded hole40 of the wall 16 for securing the lens 38 to the wall 16. Such a meansfor securing the lens 38 to the wall 16 is advantageous when the wall 16is provided with threaded holes 40, although other means for securingthe lens 38 to the wall 16 may be employed without departing from thescope of the present disclosure. Each threaded fastener 42 may be usedin combination with an associated washer 43 to protect the lens 38 whenthe threaded fasteners 42 are tightened.

The side of the lens 38 facing the wall 16 includes a groove, channel,or inset for accommodating a sealing member 44, illustrated in FIGS. 2and 2A as an annular o-ring. The sealing member 44 is positioned betweenthe lens 38 and the wall 16, such that it is tightly sandwiched betweenthe lens 38 and the wall 16 when the lens 38 is secured to the wall 16.The sealing member 44 surrounds the second bearing bore 20 and preventsleakage of oil 46 from the second bearing bore 20.

The illustrated lens 38 is generally square or rectangular, but can beany shape, provided that it is sufficiently sized to overlay the secondbearing bore 20. As the bore cap plug 22 of FIG. 1 is effectivelyreplaced by the sight window 36, the lens 38 itself provides thefunction of the bore cap plug, which is to isolate the interior of thegearbox housing 12 from the outside environment.

Once the lens 38 has been associated to the second bearing bore 20, theresulting sight window assembly 36 may be used to monitor the interiorof the gearbox housing 12. As with known sight windows, sight windowsaccording to the present disclosure may be used to monitor the level ofoil 46 in the gearbox housing 12, but positioning the sight windowassembly 36 at the second bearing bore 20 is additionally advantageousbecause one can monitor the input shaft 48 and one of the bearings 50from an end view (FIG. 2). Such a perspective is useful for detectingand assessing a number of possible problems occurring in the gearboxwithout dismantling the gearbox.

FIG. 3 illustrates a gearbox 52 which has the same gearbox housing 12 ofFIGS. 2 and 2A, but employs a different sight window assembly 54according to the present disclosure. In particular, the sight windowassembly 54 of FIG. 3 includes a lens 56 which is associated to thesecond bearing bore 20 by an assembly including a sealing member 58, alocating member 60, a cover member 62, and fasteners 42. In contrast tothe lens 38 of FIGS. 2 and 2A, the lens 56 of FIG. 3 is substantiallycircular instead of being rectangular. Additionally, the lens 56 of FIG.3 omits holes for receiving the fasteners 42, so it is not itselfdirectly fastened to the wall 16 and the other elements of the sightwindow 54 provide means for positioning the lens 56 with respect to thesecond bearing bore 20 and securing it to the wall 16.

In the illustrated embodiment, the sealing member 58 is an elastomericgasket with a generally square or rectangular outer perimeter and acircular central opening 64 which is most advantageously at least aslarge as the second bearing bore 20. Similar to the sealing member 44 ofFIGS. 2 and 2A, the sealing member 58 of FIG. 3 is adapted to bepositioned between the lens 56 and the wall 16 and tightly sandwichedtherebetween when the lens 56 is secured to the wall 16. Various gasketmaterials can be utilized, such as a natural rubber, a synthetic rubber,a resilient polymer, and so forth, preferably exhibiting elastomericproperties so as to provide a tight, leak-resistant and secure sealalong the gasket. To facilitate the tight sandwiching aspect of thesealing member, it is most advantageous for the central opening 64 ofthe sealing member 58 to be smaller than the lens 56 so that, when thelens 56 is associated to the second bearing bore 20, the perimeter ofthe lens 56 will press the sealing member 58 against the wall 16 toencircle the second bearing bore 20.

As for the illustrated locating member 60, it is provided as arelatively rigid bezel with a generally square or rectangular outerperimeter and a circular central opening 66. The outer perimeter of theillustrated locating member 60 is substantially identical to the outerperimeter of the sealing member 58, while the central opening 66 issubstantially the same size as the lens 56. The lens 56 is receivedwithin the central opening 66 of the locating member 60 to properlyposition the lens 56 with respect to the second bearing bore 20.

The cover member 62 of FIG. 3 is relatively rigid, with a generallysquare or rectangular outer perimeter and a circular central opening 68.The outer perimeter of the illustrated cover member 62 is substantiallyidentical to the outer perimeters of the sealing member 58 and thelocating member 60, while the central opening 68 is smaller than thecentral opening 66 of the locating member 60 to prevent the lens 56 fromfalling away from the gearbox housing 12. Most advantageously, thecentral opening 68 of the cover member 62 is at least the same size asthe second bearing bore 20 to maximize visibility into the gearboxhousing 12.

To assemble the components of the sight window assembly 54, the lens 56is seated within the central opening 66 of the locating member 60, withthe sealing member 58 being positioned between the locating member 60and the wall 16 and the cover member 62 being positioned outwardly ofthe locating member 60. Each of the illustrated sealing member 58,locating member 60, and cover member 62 is provided with four holes 70that are each aligned with the corresponding holes 70 of the othermembers. Each hole 70 receives a threaded fastener 42 which is matedwith the corresponding threaded hole 40 of the wall 16 for associatingthe lens 56 to the second bearing bore 20.

FIGS. 4 and 4A show yet another gearbox 72 which has the same gearboxhousing 12 of FIGS. 1-3, but employs a different sight window assembly74 according to the present disclosure. Rather than securing a lens tothe exterior of the wall 16 either directly (as in FIG. 2) or indirectly(as in FIG. 3), the sight window assembly 74 of FIG. 4 has a lens 76which is seated within the second bearing bore 20. In particular, thesight window assembly 74 of FIG. 4 includes a circular lens 76 with aperimeter which is received within an annular channel or groove 78defined along the inner perimeter of an annular sealing or grommetmember 80. The sealing member 80 is at least partially formed of anelastomeric material (for example, rubber, synthetic rubber or aresilient polymer having elastomeric properties) and is configured tofit tightly within the second bearing bore 20 which, in this illustratedembodiment, has two circumferential portions 77 and 79. Portion 77 is anouter circumferential portion sized to both receive and maintain thelens 76 in position and to also provide a seal between the secondbearing bore 20 and the lens 76. Portion 79 is an inner circumferentialportion sized to receive, for example, shaft 48 and bearings 50 (FIG.2). It will be seen that the outer circumferential portion 77 has adiameter less than that of the inner circumferential portion 79. Thesight window assembly 74 of FIG. 4 may be more advantageous than theembodiments of FIGS. 2 and 3 when the wall of the gearbox housingadjacent the second bearing bore omits threaded holes or is otherwiseunsuitable for easily securing a lens thereto.

Although the sight window assembly of each of FIG. 2, FIG. 3 and FIG. 4is shown in combination with the same gearbox housing, the principlesdescribed herein are not limited to the illustrated gearbox housing andmay be employed with other gearbox housing configurations withoutdeparting from the scope of the present disclosure. For example, FIG. 5shows a gearbox 82 with a gearbox housing 84 which is similar to thegearbox 12 of FIGS. 1-4A, but omits threaded holes surrounding thesecond bearing bore 86. The gearbox 82 of FIG. 5 includes a sight windowassembly 88 which is similar to the sight window assembly 74 of FIGS. 4and 4A in that it has a lens 90 which is seated within the secondbearing bore 86 rather than being secured to the associated wall 92.

More particularly, the sight window assembly 88 of FIG. 5 includes anannular ring member 94, which is shown in greater detail in FIGS. 6-7A.The ring member 94 is relatively rigid, being formed of a metallicmaterial in one embodiment, and has an inner surface which is adapted toseat the lens 90. To that end, the inner surface of the illustrated ringmember 94 is provided with a small annular shoulder 96 having a diametersuitably sized to orient the lens 90 and prevent it from falling intothe interior of the gearbox housing 84.

The inner perimeter of the ring member 94 further includes a pair ofinner channels or grooves 98 and 100. The first inner groove 98 ispositioned closer to the interior of the gearbox housing 84 than thesecond inner groove 100 when the ring member 94 is received by thesecond bearing bore 86, as shown in FIG. 5.

The first inner groove 98 is adapted to receive an inner sealing member102, which is illustrated as an annular o-ring. The shoulder 96 of thering member 94 is adjacent to the first inner groove 98 and positionsthe lens 90 in line with the first inner groove 98. With the innersealing member 102 in place within the first inner groove 98, the lens90 is pressed into the ring member 94 until it abuts the shoulder 96. Sopressing the lens 90 into the ring member 94 presses the inner sealingmember 102 against the first inner groove 98, thereby providing a sealbetween the ring member 94 and lens 90.

When the lens 90 has been pressed into the ring member 94, a retainingmember 104 is inserted into the second inner groove 100. In theillustrated embodiment, the retaining member 104 is a typical snap ringwith a diameter that can be temporarily decreased (e.g., using pliers)to position it within the second inner groove 100 and then returned toits original diameter to seat within the second inner groove 100. Asbest shown in FIGS. 5 and 7A, the diameter of the lens 90 is larger thanat least the inner diameter of the retaining member 104, so theretaining member 104 effectively prevents the lens 90 from falling awayfrom the gearbox housing 84. Hence, the lens 90 is trapped in placewithin the ring member 94 on opposite sides by the shoulder 96 and theretaining member 104 and on its outer perimeter by the inner sealingmember 102.

With the lens 90 secured in place within the ring member 94, the ringmember 94 may be inserted within the second bearing bore 86 of thegearbox housing 84 to form the sight window assembly 88. The ring member94 is configured to fit snugly within the second bearing bore 86 (FIG.5), but there may be slight dimensional differences therebetween,creating a small gap. To avoid oil leakage, the outer surface of thering member 94 may be provided with an outer channel or groove 106 forreceiving an outer sealing member 108, illustrated as an annular o-ring.The outer sealing member 108 is positioned between the ring member 94and the second bearing bore 86 to eliminate any gap therebetween.

FIG. 8 illustrates another gearbox 110 incorporating a sight window 112which may be advantageous for use in combination with a gearbox housinglacking threaded holes or other means for affixing a lens to the wall114 associated with the second bearing bore 116. In the embodiment ofFIG. 8, the sight window 112 includes a lens 118 and a modified bore capplug 120. The modified bore cap plug 120 of FIG. 8 is similar to thebore cap plug 22 of FIG. 1, but includes an opening 122 machined orotherwise formed in its center. The central opening 122 is illustratedin FIG. 8 as being circular, but may be any shape without departing fromthe scope of the present disclosure. Most advantageously, the centralopening 122 is relatively large to increase visibility through the sightwindow 112 and into the interior of the gearbox housing 124.

As per the design which is conventional of known bore cap plugs, themodified bore cap plug 120 includes a skirt or rim 126 extending in onedirection from its outer perimeter. The lens 118 is adapted to bereceived within the skirt 126 to ensure that the lens 118 does notinterfere with the association of the second bearing bore 116 and themodified bore cap plug 120 (via the skirt 126, per conventional design).In addition to being adapted to seat within the skirt 126, it is alsoadvantageous for the lens 118 to be sized and configured to completelyoverlay the central opening 122 to prevent leakage of oil when thecombination of the modified bore cap plug 120 and the lens 118 areassociated to the second bearing bore 116. In the illustratedembodiment, the lens 118 is substantially circular, with a diametergreater than the diameter of the circular central opening 122 and lessthan the diameter of the skirt 126. In other embodiments, the centralopening 122 and the lens 118 may be provided in non-circular shapeswithout departing from the scope of the present disclosure, providedthat the lens 118 overlays the central opening 122 when seated withinthe skirt 126.

The lens 118 is affixed to the modified bore cap plug 120 to prevent itfrom becoming dislodged during use of the gearbox 110. The lens 118 maybe affixed by any one of a variety of means such as, but not limited to,an adhesive that will not degrade upon prolonged exposure to oil orwhatever other lubricant is used in the gearbox 110. When the lens 118has been affixed to the modified bore cap plug 120, the combination issecured within the second bearing bore 116 in the same way as aconventional bore cap plug (such as the bore cap plug 22 of FIG. 1) toprovide a sight window 112.

FIGS. 9-11 show another alternative sight window assembly 128, which canbe incorporated into the gearbox housing 84 of FIG. 5, as shown in FIGS.10 and 11. Similar to the embodiment of FIGS. 4 and 4A, the sight windowassembly 128 has a lens 130 which is seated within the second bearingbore 86. In particular, the sight window assembly 128 of FIG. 9 includesa circular lens 130 with a perimeter which is received snugly within anannular channel or groove 132 defined along the inner perimeter of anannular grommet member 134.

The grommet member 134 of FIGS. 9-11 is comparable to the sealing member80 of FIG. 4 (e.g., being at least partially formed of an elastomericmaterial, such as rubber, synthetic rubber, or a resilient polymerhaving elastomeric properties). The grommet member 134 may be embossedor otherwise molded or designed to include various markings andinformation such as, for example, a company name, a part number, etc. Incontrast to the sealing member 80 of FIG. 4, the grommet member 134 ofFIG. 9 has an outer diameter less than that of the second bearing bore86. Accordingly, the grommet member 134 forms a seal around the lens130, but does not form a secondary seal against the second bearing bore86. Instead, the sight window assembly 128 is provided with a generallyannular sealing ring 136 which serves to provide a seal between thegrommet member 134 and the second bearing bore 86, as shown in FIGS. 10and 11.

As best illustrated in FIG. 11, the sealing ring 136 has a generallyL-shaped cross-section, with a first leg or surface 138 and a second legor surface 140 which are generally or substantially perpendicular toeach other. At least an outer end of the first surface 138 is receivedwithin an annular channel or groove 142 defined in the outer perimeterof the grommet member 134. The first surface 138 extends in a generallyor substantially radial direction to span the gap between the outerperimeter of the grommet member 134 and the second bearing bore 86. Thesecond surface 140 has a curvature matching that of the second bearingbore 86 and forms a friction fit therein when the sealing ring 136 ispressed into the second bearing bore 86.

The sealing ring 136 is a composite component, being comprised of arelatively rigid base 144 (formed of a metallic material in a preferredembodiment) and a softer coating layer 146 (formed of an elastomeric orrubber material in a preferred embodiment). The base 144 and coatinglayer 146 may be joined by any suitable means, including known means forapplying an elastomeric coating to a metallic piece of material.

In the illustrated embodiment, the coating layer 146 coverssubstantially the entire outer side of the base 144 (i.e, the portion ofthe first surface 138 which faces away from the gearbox housing and theportion of the second surface 140 which abuts the second bearing bore 86when the sealing ring 136 is installed within the second bearing bore86). However, in other embodiments, the coating layer 146 may cover onlya portion of the outer side of the base 146 and/or some or all of theinner side of the base 144 (i.e., the portion of the first surface 138which faces toward the interior of the gearbox housing and the portionof the second surface 140 which faces the central axis of the secondbearing bore 86 when the sealing ring 136 is installed within the secondbearing bore 86). By such a composite configuration, the sealing ring136 is sufficiently rigid to hold the grommet member 134 in place withinthe second bearing bore 86 (in the orientation of FIGS. 10 and 11),while being sufficiently soft at the location(s) of the coating layer146 to provide a fluid-tight sealing surface.

Although the sight window assembly of FIGS. 9-11 is shown in combinationwith the gearbox housing of FIG. 5, it should be understood that it maybe used in combination with other gearbox housings (including thegearbox housing 12 of FIG. 1) without departing from the scope of thepresent disclosure.

It will be understood that the embodiments described above areillustrative of some of the applications of the principles of thepresent subject matter. Numerous modifications may be made by thoseskilled in the art without departing from the spirit and scope of theclaimed subject matter, including those combinations of features thatare individually disclosed or claimed herein. For these reasons, thescope hereof is not limited to the above description but is as set forthin the following claims.

1-20. (canceled)
 21. A gearbox for an engine-driven mechanism,comprising: a gearbox housing having opposing walls; a first bearingbore defined in one of said opposing walls and adapted for receiving ashaft; a second bearing bore defined in the other opposing wall andaligned with the first bearing bore, the second bearing bore rotatablyreceiving said shaft, the second bearing bore having a perimeter with aperimeter size; a sight window assembly associated with the secondbearing bore, the sight window assembly comprising an annular grommet,an annular ring and a generally transparent and/or translucent lenshaving a perimeter; said annular grommet has a first annular channelbeing of a first perimeter size supporting the lens and a second annularchannel being of a second perimeter size, the second perimeter sizebeing less than the perimeter size of the second bearing bore andgreater than the lens perimeter; the annular ring and the grommet secondannular channel are in engagement, and the sight window assembly isconfigured to be at least partially received within and provide a sealwith said second bearing bore; and whereby the sight window assembly isa sight window for the gearbox at the second bearing bore.
 22. Thegearbox according to claim 21, wherein the annular grommet spans a gapbetween the lens perimeter and the second bearing bore perimeter. 23.The gearbox according to claim 21, wherein the annular ring supports theannular grommet, and the annular grommet and annular ring togetherprovide a friction-fit seal between the lens and the second bearingbore.
 24. The gearbox according to claim 21, wherein the annular grommetis an elastomeric material and the annular ring is metallic.
 25. Thegearbox according to claim 21, wherein the annular grommet comprises anelastomeric grommet portion having said first and second annularchannels and an elastomeric layer portion over at least part of theannular ring, and the annular ring is metallic.
 26. The gearboxaccording to claim 21, wherein the annular ring is generally L-shaped incross-section with a first leg in engagement with the grommet secondannular channel and a second leg generally perpendicular to the firstleg and generally parallel and spaced closely with respect to the secondbearing bore.
 27. The gearbox according to claim 26, wherein the annulargrommet comprises an elastomeric grommet portion having said first andsecond annular channels and an elastomeric layer portion over at leastthe second leg of the annular ring, whereby said elastomeric layerportion is between the second leg of the annular ring and the secondbearing bore.
 28. The gearbox according to claim 21, wherein the secondbearing bore has an inner circumferential portion sized to receive theshaft and an outer circumferential portion sized to receive the sightwindow assembly.
 29. The gearbox according to claim 28, wherein saidouter circumferential portion and said inner circumferential portion areof substantially the same diameter.
 30. The gearbox according to claim28, wherein said outer circumferential portion has a diameter less thanthat of the inner circumferential portion.
 31. A gearbox for anengine-driven mechanism, comprising: a gearbox housing having opposingwalls; a first bearing bore defined in one of said opposing walls andadapted for receiving a rotating shaft; a second bearing bore defined inthe other opposing wall and aligned with the first bearing bore, thesecond bearing bore adapted for rotatably receiving the rotating, thesecond bearing bore having a perimeter with a perimeter size; a sightwindow assembly associated with the second bearing bore, the sightwindow assembly comprising an annular elastomeric member, an annularrelatively rigid ring and a generally transparent and/or translucentlens having a perimeter; said annular elastomeric member has a firstannular channel being of a first perimeter size supporting the lens anda second annular channel being of a second perimeter size, the secondperimeter size being less than the perimeter size of the second bearingbore and greater than the lens perimeter; the annular relatively rigidring and the elastomeric member second annular channel are inengagement, and the sight window assembly is configured to be at leastpartially received within and provide a seal with the second bearingbore; and whereby the sight window assembly is a sight window for thegearbox at the second bearing bore.
 32. The gearbox according to claim31, wherein the annular elastomeric member spans a gap between the lensperimeter and the second bearing bore perimeter.
 33. The gearboxaccording to claim 31, wherein the annular relatively rigid ringsupports the annular elastomeric member, and the annular elastomericmember and annular relatively rigid ring together provide a friction-fitseal between the lens and the second bearing bore.
 34. The gearboxaccording to claim 31, wherein the annular elastomeric member comprisesan elastomeric grommet portion having said first and second annularchannels and an elastomeric layer portion over at least part of theannular relatively rigid ring, and the annular relatively rigid ring ismetallic.
 35. The gearbox according to claim 31, wherein the annularrelatively rigid ring is generally L-shaped in cross-section with afirst leg in engagement with the grommet second annular channel and asecond leg generally perpendicular to the first leg and generallyparallel and spaced closely with respect to the second bearing bore. 36.The gearbox according to claim 35, wherein the annular elastomericmember comprises an elastomeric grommet portion having said first andsecond annular channels and an elastomeric layer portion over at leastthe second leg of the annular relatively rigid ring, whereby saidelastomeric layer portion is between the second leg of the annularrelatively rigid ring and the second bearing bore.
 37. The gearboxaccording to claim 36, wherein the annular elastomeric member covers atleast substantially all of outwardly facing surfaces of the annularrelatively rigid ring.
 38. The gearbox according to claim 31, whereinthe second bearing bore has an inner circumferential portion sized toreceive the shaft and an outer circumferential portion having saidperimeter size that is sized to receive the sight window assembly,wherein said outer circumferential portion and said innercircumferential portion are of substantially the same diameter orwherein said outer circumferential portion has a diameter less than thatof the inner circumferential portion.
 39. A gearbox for an engine-drivenmechanism, comprising: a gearbox housing having opposing walls; a firstbearing bore defined in one of said opposing walls and adapted forreceiving a shaft; and a sight window assembly comprising: a secondbearing bore defined in the other opposing wall and aligned with thefirst bearing bore, a bore cap plug having an opening in its centralarea and a rim extending in one direction from its outer perimeter, anda generally transparent and/or translucent lens associated with thesecond bearing bore; and wherein the bore cap plug has a rim extendingin one direction from its outer perimeter, the lens being adapted to bereceived within the rim, and the lens overlying the central area openingand being affixed to the bore cap plug.
 40. The gearbox according toclaim 39, wherein the lens is substantially circular and has a diametergreater than the diameter of the bore cap plug opening, the lensdiameter being less than the diameter of the rim of the bore cap plugsight window assembly.
 41. The gearbox according to claim 40, whereinthe diameter of the rim of the bore cap plug is substantially the sameas the diameter of the second bearing bore.
 42. The gearbox according toclaim 39, wherein said second bearing bore has an inner circumferentialportion sized to receive the shaft and an outer circumferential portionsized to receive the rim of the bore cap plug, wherein the lens is atleast partially within the outer circumferential portion of the secondbearing bore.
 43. The gearbox according to claim 42, wherein said outercircumferential portion and said inner circumferential portion are ofsubstantially the same diameter.
 44. The gearbox according to claim 42,wherein said outer circumferential portion has a diameter less than thatof the inner circumferential portion.
 45. The gearbox according to claim39, wherein the lens is at least partially positioned within the secondbearing bore.